This invention relates generally to a discharge valve assembly for a trigger actuated pump sprayer, and more particularly to such a valve assembly as having a product retraction feature to avoid the formation of dribbles and drips of liquid product at the discharge orifice when in use. Another feature of the invention provides for reducing the volume of the discharge passage leading from the pump chamber to the discharge orifice to aid in pump priming.
Trigger actuated pump sprayers are known to have certain basic features, namely, a trigger actuated piston operating in a rump cylinder, a valve controlled inlet leading to the pump chamber, and a valve controlled discharge leading away from the chamber. During each piston return stroke, the internal pump pressure falls below atmospheric as the pump chamber volume expands to thereby induce the flow of liquid product into the chamber from the container through the inlet via an unseated inlet check valve. The pump chamber is thus charged (or primed) and recharged with liquid product during each suction stroke. And during induction of the product the discharge check valve is drawn closed against its valve seat to both seal the discharge closed and to facilitate pump priming. During each pressure stroke product is discharged from the pump chamber thereby sealing the inlet closed as the inlet check valve is forced against its valve seat, while applying pressure against the discharge check valve to move it from its valve seat to thereby open the discharge to the orifice at the exit end thereof. Examples of the known pump sprayers are: Model No. TS-800 manufactured by Calmar Inc.; U.S. Pat. No. RE 33,235; 4,527,741; 5,234,166; and 5,509,608.
Oftentimes residual product in the discharge passage leading to the exit opening tends to accumulate at the discharge orifice after the closing of the discharge valve thereby forming dribbles and drips (product drooling) at the orifice, which is undesirable.
The trigger sprayer is typically structured as having a relatively long discharge barrel leading from the pump chamber to the discharge orifice at the nozzle end thereof. The discharge barrel defining the discharge passage is formed integrally with the pump body during the molding operation and is thus sized sufficiently to facilitate ease in molding. The diameter and length of the discharge passage, however, provides a volume which fills with product during the pumping operation and remains substantially filled during use. When the pump chamber is primed liquid product is drawn into the pump chamber during each return stroke incrementally and is discharged from the chamber during each pressure stroke into the discharge flow path which extends between the outlet from the pump chamber to the discharge orifice. During the initial pressure strokes the discharge path is gradually filled with product and it is the strokes-to-prime ratio which is one of several factors determining pump performance.
The volume reduction of the discharge passage has been found a factor in reaching an acceptable strokes-to-prime ratio, as less volume is required to be occupied by product during the initial pressure strokes, thereby effecting an earlier discharge through the orifice.